In a semiconductor device manufacturing process, a batch type heat treatment system has been used to collectively perform a film formation processing, an oxidation processing, a diffusion processing, and the like on a plurality of workpieces such as, for example, semiconductor wafers. In the batch type heat treatment system, the semiconductor wafers may be efficiently processed. However, it is difficult to ensure uniformity of the heat treatment of the plurality of semiconductor wafers.
In order to solve the problem, for example, Japanese Patent Laid-Open Publication No. 2005-183596 has proposed a heat treatment apparatus for automatically adjusting a temperature of an external air taken into a heater chamber to be constant.